1. Technical Field
The present invention relates to an inflatable vehicle occupant restraint device. In particular, the present invention relates to an inflator for inflating an air bag.
2. Description of the Prior Art
Inflators for air bag systems having inflation fluid stored under pressure are known. PCT Publication 91/11347 discloses one such inflator. The inflator includes a housing defining a pair of closed chambers. One chamber stores an inflation fluid under pressure and the other chamber houses an igniter. A closure disk blocks fluid communication between the two chambers. The igniter is actuatable to move a member which breaks the closure disk to allow the inflation fluid to flow from the one chamber into an air bag.
Another inflator is disclosed in U.S. Pat. No. 5,184,846 and includes a container which stores an inflation fluid. An ignition chamber contains an ignitable propellant materials. The propellant material, when ignited, produces combustion products including heat and gas for augmenting the gas in the container. The ignition chamber is closed by a piston which blocks fluid communication between the propellant material in the ignition chamber and the gas in the container. An igniter ignites the propellant material upon the occurrence of a vehicle collision. The resulting combustion products cause the gas pressure in the ignition chamber to increase to an elevated level. The gas pressure in the ignition chamber then moves the piston into an actuated position. When the piston moves into the actuated position, it opens the container to release the gas to flow from the container to the vehicle occupant restraint. The piston also opens fluid communication between the ignition chamber and the container.
Another inflator disclosed in U.S. patent application Ser. No. 08/409,871, filed Mar. 24, 1995, which is a continuation of Ser. No. 08/110,159, filed Aug. 20, 1993, includes a pressure vessel, an ignitable material and a cup member. The pressure vessel defines a sealed storage chamber containing inflation fluid for inflating the inflatable device. The pressure vessel further has a closure wall which is rupturable to open an outlet opening through which the inflation fluid flows outward from the storage chamber. The ignitable material produces combustion products including heat for heating and pressurizing the inflation fluid in the storage chamber.
The cup member is located radially inward of a ring shaped portion of the storage chamber, and has a piston which is movable between an unactuated position and an actuated position. The piston of the cup member includes a plunger for rupturing the closure wall upon movement of the piston from the unactuated position to the actuated position. The cup member further has a rupturable portion which holds the piston portion in the unactuated position.
The apparatus further includes an igniter for igniting the ignitable material and for causing pressure to develop a thrust against the cup member. The thrust ruptures the rupturable portion of the cup member, and propels the piston portion of the cup member from the unactuated position to the actuated position.